This invention relates to apparatus for controlling the application of microwave energy to chemically treated cellulosic fabric.
Processes have been developed in the textile industry to try to chemically treat fabric in an aqueous solution of poly functional/agent so as to impart a memory of wrinkle resistant capability. The curing process or the application of various forms of energy has been given much attention. The application of too much heat results in severe degradation, hot spots or burned areas and yellowing of the monomers or cross-linkable polymers, particularly in light colored garments or fabric. Too little heat energy applied results in a less than desirable wrinkle resistant capability after very few washes.
In U.S. Pat. No. 3,846,845, Englert et al., there is described a method of curing chemically treated cellulosic fabric with microwave as the primary energy source for affecting the cure. While this process has distinct advantages over the high temperature, long duration cure ovens most commonly used in the industry, it has not been used or has not achieved commercial success or acceptance.
For three decades the apparel industry has worked to give natural fibers and blends an easy care finish. That finish would allow the consumer to launder and wear the garment with little or no ironing.
Several chemicals are available to impart an easy care property to fabrics. The only way users have been able to set the "crease" or the smooth fabric appearance and property is to bake the finished, pressed garments in either an enclosed oven or one designed on the tunnel concept that allows continuous movement of garments.
That heat, usually 325.degree. for 10-15 minutes, sets the creases and fabric smoothness, but also the heat breaks down the fiber, which shortens normal wearing life.
The old heat set process was first developed in the 1960's. It was subsequently abandoned until recently. The chemicals, and the high heat necessary to activate them, broke down the fibers so much that they lost their tensile strength, as much as 40% in most processes. That reduced the life of the garments. In that process the garment has to be pressed as wanted to look when "finished". That required an oven in a facility that also could do the pressing. Once the finished press was done, movement would or could cause wrinkles that would become permanent, once cured in the oven. The high cost of installing process ovens made them available only to a few producers. The time it takes to "bake" in the conventional ovens, 10-15 minutes, also limits their ability to do the number of units that may be needed.
The garment industry is a highly competitive industry. Costs must be carefully controlled. High costs of installation, costs of space for ovens, costs of isolating workers from the high oven heats, and costs of operating the ovens, all translated to higher garment unit costs. Permanence of oven installations made factory modernization more difficult.
Heat treatment ovens are large and expensive to build and to operate. Once built, the ovens cannot be conveniently moved. Factory designs and locations are made inflexible, and building or relocating heat treatment ovens is a major cost in moving and relocating and redesigning garment production facilities.
A need exists for a press setting method and apparatus that will economically and effectively permanently set creases and fabric smoothness without destroying garment life and without restricting factory design and location.